Apple has started assembling a team of people specializing in fitness, medical sensors, manufacturing, and hardware and software engineering in order to produce a fitness-focused wearable computer chock full of sensor technology, sources say. Apple is stated to have experimented with a number of designs in the past, including ones that could clip onto clothing, like an iPod shuffle. Currently though the company is thought to have returned to a wrist-wrapped device, likely the iWatch.

Worldwide marketing head Phil Schiller and his team have reportedly been examining competing wearable devices, like the Jawbone Up. Apple's executive staff are also intimately familiar with Nike's FuelBand. CEO Tim Cook has been seen wearing the device, as has senior VP of Technologies Bob Mansfield. Cook is on the Nike board of directors, and Mansfield is believed to be at the heart of Apple's wearable computer efforts. Before Apple's Technologies division got started last fall, Mansfield was allegedly working on health appliances.

The iWatch team is thought to be working in buildings separate from Apple's headquarters at 1 Infinite Loop in Cupertino. Helping to lead the project with Mansfield are VP Kevin Lynch, and senior hardware director James Foster. The sources elaborate that Lynch's group is concentrating on software, while Foster's section is developing the underlying mechanics and technologies. Despite a nominal division, the two units are thought to have close ties.

It's speculated that the iWatch team is probably working other Apple units, like Jonathan Ive's Industrial Design team. Foster's group, though, is said to have experts in areas like chips, sensors, and battery/power efficiency. Apple is in fact claimed to have gathered together battery experts from multiple divisions, for example pulling engineers from the Mac section to work on power efficiency. One source adds that Apple has recruited former iPhone engineers who worked on the assembly and miniaturization of internal components for the original iPhone.

On top of this, some people absorbed into Apple through its buyout of AuthenTec are also involved in the iWatch team. The sources say that Apple has been experimenting with fingerprint sensors that could be embedded on top of a device or even within a display; in the latter case, though, the technology is thought to be years off. A fingerprint reader may or may not make it into an iWatch.

Some of the team is devoted to SoC (system-on-chip) work. That aspect is especially important, as a thin, wearable device needs a small and extremely power-efficient processor. Beyond people from Mansfield's semiconductor unit, Apple has allegedly poached workers from chip design firms like XMOS and Infineon.

An unusual aspect of the project is that Apple has hired people from companies specializing devices that can analyze sleep patterns. In general though the device is believed to be oriented around fitness; people on the team have patents for things like light and distance sensors, and integrating mobile gadgets with fitness equipment. Recent hires have included scientists and executives from sensor developers including AccuVein, C8 MediSensors, and Senseonics. AccuVein and C8, notably, are known for non-invasive detection methods; any vital statistics tracking in an iWatch would have to be non-invasive.

C8 actually broke up in February, according to ex-CTO Rudy Hofmeister, because the company was having trouble getting consistent glucose level readings. Apple then immediately pursued several former C8 directors, engineers, designers, and scientists, including people familiar with machine learning. An anonymous source claims that even before C8 dissolved, Apple was considering buying the firm for its technology and resources.

From Senseonics Apple has allegedly poached "at least one" high-profile person to work on biometric sensors. That person is VP of product development Dr. Todd Whitehurst, who Senseonics confirms went to Apple at the beginning of July. Senseonics' own technology requires embedding a capsule into the body, but Apple is more likely interested in the accompanying wearable transmitter, which can interact with the capsule via Bluetooth, and transmit data to a smartphone app.

One rumor is that one of the fitness experts is Jay Blahnik, a consultant and educator. Blahnik's website states that he helped develop Nike initiatives such as the FuelBand, Nike+Running, and the Nike Training Club, including the Nike Training Club app.

When an iWatch might ship is still in the air. Rumors once had it shipping as soon as this fall, but more recent claims have pushed it into 2014. One setback was the departure of a team member to Google X, the "black" Google section responsible for things like Glass, potentially the iWatch's main competition.